1. Field of the Invention
The present invention relates generally to the field of variable-displacement compressors for use in air conditioning apparatus. More particularly, the present invention is directed towards variable-displacement compressors employing means for determining the torque for determining a torque of the compressor.
2. Description of the Related Art
An externally controlled, variable-displacement compressor, e.g., a swash plate-type, variable-displacement compressor, may be employed in a refrigeration circuit of a vehicular air conditioning apparatus. In operation, a refrigerant may be introduced into a crank chamber via a discharge chamber, and the amount of refrigerant introduced into the crank chamber may be controlled by an external signal operating a control valve. Moreover, a magnitude of a displacement of the compressor may correspond to a refrigerant pressure within the crank chamber, and an inclination angle of a swash plate may vary in accordance with the refrigerant pressure. As such, the external signal may control the magnitude of the displacement of the compressor.
An objective magnitude of displacement of the compressor may depend on a magnitude of a load of the air conditioning apparatus, i.e., a magnitude of a torque load of the compressor. Nevertheless, the magnitude of the torque load may vary over time. Consequently, in order to control the displacement of the compressor, the magnitude of the torque of the compressor may be monitored during operation of the compressor.
A known method of determining the magnitude of the torque of the compressor includes indirectly calculating the magnitude of the torque based on magnitudes of various detectable parameters related to the refrigeration circuit. Such detectable parameters may include suction pressure, suction temperature, and discharge pressure of the compressor.
Japanese Patent Publication No. Hei 5-164045 describes a method for directly detecting the magnitude of the torque of the compressor by sensing a magnetostriction, e.g., the dependence of the state of strain of a ferromagnetic element on the direction and strength of its magnetization, of a magnetic membrane which is entwined around a drive shaft of the compressor and includes a slight twisting deformation. Nevertheless, because magnetic detectors are assembled into a cylindrical portion of front housing, inclusion of the magnetic detectors increases a cost associated with the manufacture of the compressor.
Therefore, a need has arisen for compressors, and methods of employing such compressors, which overcome these and other disadvantages of the related art. A technical advantage of the present invention is that a compressor includes means for detecting a time differential between a first timing signal generated by a first sensor and a second timing signal generated by a second sensor, such that a torque of the compressor may be determined based on the time differential.
In an embodiment of the present invention, a compressor, e.g., a variable-displacement compressor, is described. The compressor comprises a front housing, a cylinder block, a cylinder head, and a torque transmission mechanism. The torque transmission mechanism comprises a pulley, a plate-shaped elastic member connected to the pulley, a hub connected to the plate-shaped elastic member, a drive shaft connected to the hub, and a rotor connected to the drive shaft. The compressor also comprises a reciprocating mechanism connected to the torque transmission mechanism. The compressor further comprises means for determining, e.g., calculating, detecting, measuring, or the like, a torque of the compressor. The means for determining comprises a first marker affixed to the pulley and a second marker affixed to the hub. In a variation of this embodiment, the second marker is affixed to the drive shaft. Moreover, a circular deformation of the plate-shaped elastic member creates an angular offset between the first marker and the second marker. The means for determining also comprises a first sensor affixed to the front housing which generates a first timing signal when the first marker is positioned within substantially the same vertical plane as the first sensor. The means for determining further comprises a second sensor which generates a second timing signal when the second marker is positioned within substantially the same vertical plane as the second sensor. When second marker is affixed to the hub, the second sensor is affixed to the front housing. Nevertheless, in the variation of this embodiment, when the second marker is affixed to the drive shaft, the second sensor is positioned within a center bore of the cylinder block. Further, there is a time differential between when the first marker is positioned within substantially the same vertical plane as the first sensor and when the second marker is positioned within substantially the same vertical plane as the second sensor. Moreover, the time differential corresponds to the angular offset and the torque of the compressor is determinable from the time differential.
In another embodiment of the present invention, a method of determining a torque of a compressor is described. The method comprises the steps of affixing a first marker to a pulley and affixing a second marker to a hub. In a variation of this embodiment the method includes the step of affixing the second marker to a drive shaft. Moreover, a circular deformation of a plate-shaped elastic member, which is affixed to the hub and also is affixed to the pulley, creates an angular offset between the first marker and the second marker. The method also comprises the steps of affixing a first sensor to a front housing, and affixing a second sensor to the front housing when the second marker is affixed to the hub. In the variation of this embodiment, the method comprises the step of positioning the second sensor within a cylinder bore of a cylinder when the second marker is affixed to the drive shaft. The method further comprises the steps of generating a first timing signal when the first marker is positioned substantially within the same vertical plane as the first sensor, and generating a second timing signal when the second marker is positioned substantially within the same vertical plane as the second sensor. The method also comprises the step of determining, e.g., calculating, detecting, measuring, or the like, the torque of the compressor. The torque of the compressor is determined based on a time differential between when the first marker is positioned within substantially the same vertical plane as the first sensor and when the second marker is positioned within substantially the same vertical plane as the second sensor.
Other objects, features, and advantages will be apparent to persons of ordinary skill in the art in view of the following detailed description of the invention and the accompanying drawings.